Energy expenditure of stroke patients during upright standing

Purpose: To study the energy expenditure needed for balance control of stroke patients during upright standing, and to determine the relationship between energy expenditure and measures of balance control and muscle activity. Methods: Ten stroke patients and twelve healthy controls performed four upright standing tasks; one without and three with balance perturbations. Energy expenditure was assessed using a pulmonary gas measurement system. Conventional and dynamic balance measures were calculated from center of pressure time series, obtained with a force plate. Muscle activity of the ankle plantar flexors and dorsal flexors was measured using electromyography. Results: On average, energy expenditure during standing was 125% higher in stroke patients. Challenging balance caused a significant increase in energy expenditure (21-52%) for both groups, but no significant interaction (group x condition) was found. Balance control was impaired and muscle activity was higher in stroke patients in all standing conditions. Significant, though moderate to low, correlations were found between energy expenditure and measures of balance control and muscle activity. Conclusion: This study shows that the increased effort for maintaining balance can have a clinically relevant effect on energy expenditure of stroke patients. Besides balance control, other factors responsible for the increased energy expenditure during upright standing in stroke patients should be explored.